Anti-knock gasoline containing hydrogenated quinolines and indoles



United States Patent 2,881,061 ANTI-KNOCK GASOLINE CONTAINING HYDRO-GENATED QUINOLINES AND INDOLES James A. Brennan, Camden, N.J., andCharles C. Price,

Lansdowne, Pa., assignors to Socony Mobil Oil Company, Inc., acorporation of New York No Drawing. Application March 12, 1956 SerialNo. 570,712 12 Claims. (Cl. 44-63) This invention relates generally toimproved fuels for internal combustion engines of the spark-ignitiontype. More particularly, it is concerned with the provision of gasolineshaving improved anti-knock properties.

It is now well known that knock in spark-fired engines is due to therelatively slow oxidation of the endgas prior to the arrival of theflame front, the immediate (cause being the extremely rapid combustionof the last ,"part of the charge to burn. It is also known that certain:factors such as fuel/air ratio, compression ratio, spark :setting,engine speed, etc., affect the fuel combustion. Furthermore, it has beendetermined that the most economical burning of the gasoline is obtainedat the higher compression ratios. The higher the compression ratio,however, the higher the octane number of the gasoline necessary forknock-free operation. Because the design of modern automobile engines,particularly in recent years, has been towards increased compressionratios, the demand has been for gasolines of constantly improvedanti-knock quality. Refiners have kept abreast of this demand through(a) the development of new refining techniques, such as alkylation,isomerization, catalytic cracking, reforming, etc., and (b) the use ofanti-knock agents which are added to the gasoline. As is well known,either or both of these means can be used to improve the anti-knockquality of gasoline fuels. The present invention is concernedparticularly with the improvement of gasoline octane rating by means ofaddition agents.

Anti-knock agents most widely used in the past have been those of theso-called metallic type, of which a prime example is tetraethyl lead. Ithas been recognized, however, that the use of metal-containinganti-knock agents, such as tetraethyl lead, contributes to otherdifliculties associated with the operation of high compression engines,such as spark plug fouling, preignition, etc., which have been found tobe due to the formation of metallic deposits on the engine parts. Theart has, therefore, turned to the development of non-metallic antiknockagents which can be used either alone or in conjunction withmetallic-type anti-knock agents. The use of such non-metallic compoundsin the gasoline in conjunction with metallic anti-knock agents reducesthe formation of the deleterious metallic deposits in the engine; or, ifthe non-metallic agent is used as the sole anti-knock additive themetallic deposits are eliminated entirely.

The best presently known non-metallics are aniline and certain alkylderivatives thereof. These compounds vary greatly in their ability tosuppress knock. The class as a whole is represented by the followingstructural formula:

where R, R and R" represent hydrogen or lower alkyl groups. If either Ror R, or, both, are hydrogemsthe alkyl or alkoxy groups,

2,881,061 Patented Apr. 7, 1959 substance has knock-inhibitive ability,R and R are alkyl groups the compound has no anti-knock property.Probably the best known non-metallic is N-methylaniline. In the serieswhere R and R" are hydrogen and R is alkyl, a decrease in anti-knockeffectiveness with increasing length of the alkyl group occurs. The datain the following table illustrates the foregoing.

whereas if both ASTM Designation D908-53, ASTM Manual of Engine TestMethods for Rating Fuels, 1953 supplement.

AS'IDM Primary Reference Fuel (60% iso-octane40% n-heptane).

A recent publication by J. E. Brown et al., Ind. and Eng. Chem. 47, 2141(1955), summarizes the known information on amine type anti-knocks.These authors state that the substitution of groups larger than methylin the ortho position in aniline results in decreased antiknockefiectiveness. Furthermore, they have shown that the substitution ofonly one ortho-methyl group in N- methylaniline will cause decreasedeifectiveness.

It has now been found, however, that if the N-alkyl group is made toform a ring attached to the benzene ring ortho to the amine function,the resulting substance is an This compound is an anti-knock equal ineffectiveness to N-methyl aniline. Furthermore, replacement of thenuclear hydrogens of the aromatic ring with lower alkyl or alkoxygroups, such as methyl or methoxy groups, has been found not to lowerthe anti-knock effectiveness of the compound at all when thesubstitution is meta (5 or 7) or para (6) to the amine function and thereduction is only slight when the replacement is in the ortho (8)position. Substitution of the non-aromatic ring by lower does decreasethe anti-knock activity somewhat, however, the resulting compounds arestill highly effective anti-knock agents.

It will be appreciated from the foregoing, that the present inventionprovides an entirely new class of compounds having anti-knock ability.It is, therefore, the principal object of this invention to provide anew class of non-metallic anti-knock agents. It is a further object toprovide improved I these new anti-knock agents. Other and furtherobjects will become apparent from the following description of theinvention.

Broadly, the compounds of the invention are defined by the followinggeneral formula:

12-0 0 c n-i: ii La gasoline compositions containingwhere R is selectedfrom-.the.-group consisting of hydrogen, alkyl groups having from 1 toabout 4 carbon atoms These compounds are dihydroindoles.

Specific examples of compounds of the character contemplated by thisinvention include the following (py =pyridine).

(a) Py-tetrahydroquinolines such as: py-tetrahydroquinoline;.2-methyl-py-tetraquinoline; 2,4-dimethyl-pytetraquinoline;2,2,4-trimethyl-py-tetraquinoline; 4-ethy1- py-tetraquinoline;4,6-diethyl-py-tetraquinoline; 4,5,6-tripropyl-py-tetraquinoline;4,5,6-tributyl-py-tetraquinoline; 6methyl-py-tetrahydroquinoline;8-methyl-py-tetrahydro quinoline; 2methyl-6-methoxy-py-tetrahydroquinoline;

2-methyl-6-butoxy-py-tetrahydroquinoline; and, 6-methyl,

8-methoxy-py-tetrahydroquinoline.

(b) Dihydroindoles such as: Z-methyldihydroindole; 3-ethyldihydroindole;5-methoxydihydroindole; G-methyldihydroindole; 3-ethyldihydroindole;5-propyldihydroindole; S-butyl-dihydroindole; S-butoxydihydroindole;wandZ-methyl-6-butyldihydroindole.

The py-tetrahydroquinoline;compounds of the invention can be prepared bya variety of methods. The reduction of the pyridine ring inquinoline oralkyl-substituted quinolines by either catalytic or chemical means isthe preferred method of synthesis. Procedures for this reduction maybefound in the literature. A typical reduction is given in Example III,below. The dihydroindoles, on the other hand, may be-convenientlyprepared by any of the known methods, such as the catalytic reduction ofindole or appropriately substituted indoles.

The following examples and test results will serve to further illustratethe present invention.

Example I.-Py-tetrahydroquinoline as white label re- C. It had the fol-This compound was purchased agent. Its melting point is 15-l6 lowinganalysis:

Example l1.-Acetne-Anil CHI 4 Prepared from aniline and acetone in thepresence of iodine according to W. RJ'Vaughan, Org. Syn. 28, 49

(1948). Its boiling point is131132 C. at 13 mm.

Example Ill.-2,2,4-trimethyl-py-tetrahydr0quin0line i CH;

Twenty grams (0.116 mole) of acetone-anil were dissolved in 250milliliters of absolute alcohol. Twenty grams (0.87 g. atom) of sodiumwere added at such a rate as to maintain steady reflux. Near the end ofthe metal addition it became necessary to heat the mixture to maintainrapid reaction, After all the sodium had been added, the reactionmixture was refluxed an additional two hours. The solution was cooled toroom temperature (crystalline solid), dissolved in water, made acid with6 N HCl and most of the alcohol removed by distillation. The residue wasmade basic with concentrated NaOH then extracted with ether. The com-.bined ether extracts were dried over anhydrous Na SO After removal ofthe ether, the residue was distilled at reduced pressure, yielding 15grams of a colorless oil, with a boiling point of 108-110 C. at 8-9 mm.

Example IV.2,4-dimethyl-py-tetrahydroquinoline 2,4-dimethylquinoline wasprepared from acetone-anil (W. R.Vaughan, ibid.). The quinoline was thenreduced as described in Example HI. The boiling point of2,4-dimethyl-py-tetrahydroquinoline is 126130 C. at i 11 mm.

Example V.--2-methyl-py-tetrahydroquinoline Prepared by the reduction ofZ-methyl-quinoline as described in Example 111. Thereduced quinolineboils at .110113 C. at 3-4 mm.

Example VI.-6-methyl-py-tetrahydroquinoline Prepared from6-methyl-quinoline by reduction with sodium and alcohol (Example III).The product had a boiling point of 93-96 C. at 3-4 mm.

Example VIl.8-methyl-py-tetrahydroquinoline CH3 H Prepared by thereduction of S-methyl-quinoline as described-in Example III.8-methyl-py; t etrahydroquipQ-. ueeiboikat 1341 0. m

Example VIIL-ti-methoxy-py-telrehydroquinoline CHsO This compound waspurchased as white label reagent. Its melting point is 40-42 C.

ANTI-KNOCK ABILITY Fuel blends of the compounds described in theforegoing examples were prepared and the Research octane numbers thereofwere determined. The pertinent data and the results obtained arerecorded in Table II. These data show that all of thepy-tetrahydroquinolines are octane improvers and that this improvementapplies in both clear and leaded fuels.

It will be seen from the table that acetone-anil (Example H), whichdiffers from the py-tetrahydroquinolines only by an olefinic bond in thenon-aromatic ring, is a pro-knock. The reduction of this bond results in2,2,4- trimethyl-py-tetrahydroquinoline (Example HI), a substance withanti-knock properties.

TABLE II Amount of Research additive octane number Compound added WeightMole 3 cc.

perper- Clear TEL/ cent cent gal.

Base fuel 1 60.0 84. 3 N -methylaniline 3 3. 3 78. 93. 4py-Tetrahydroquinollne (Ex. I) 3 2. 7 77.3 94.4 Acetone-anll (Ex. II) 32.0 48.3 79.1 2,2,4-trimethyl-py-tetrahydroquinoline (Ex. II 3 2.0 64.86.3 2,4-dtmethyl-py-tetrahydroquinoline (Ex. IV) 3 2. 3 70. 7 88. 3Z-methyI-p ttrahydroquinollne (Ex. 3 2. 5 72. 2 90. 5 S-methyl-ptrahydroquinoline (Ex. I) 3 2. 5 74. 6 6-methyl-py-tetrahydroquinoline(Ex. VII 3 2. 5 77. 5 93.1 6 methoxy py tetrahydroqulnoline (Ex. VIII) 32. 2 78.0 92. 5

1 ASIM primary reference fuel: 60/40 lsooctanelmheptane.

Also, it will be seen that the substitution of methyl groups in theparent compound affects its anti-knock properties. Thus,2,2,4-trimethyl-py-tetrahydroquinoline (Example III) was the poorestanti-knock of the series. The removal of one of the methyl groups in2,2,4-trimethyl-py-tetrahydroquinoline, however, results in the2,4-dimethyl derivative and an increase in anti-knock effectiveness(Example IV). Also, Z-methyl-py-tetrahydroquinoline (Example V) wasfound to be superior, as an anti-knock, to the 2,4-dimethyl derivative.The parent compound was better than any of its methyl derivatives, whenthe methyl was substituted in the non-aromatic ring.

Methyl substitution in the 8-position of the aromatic ring lowered theanti-knock effect of py-tetrahydroquinoline somewhat as shown by8-rnethyl-py-tetrahydroquinoline (Example VI). Methyl substitution inthe 6-position, however, resulted in an anti-knock comparable topy-tetrahydroquinoline on a weight basis (Example VII).

The py-tetrahydroquinoline (Example I) was 10% better on a mole basisand the 8-methyl derivative (Example VI) was identical in effectivenessto N-methylaniline. The 6-methyl-py-tetrahydroquinoline (Example VII)and 6-methoxy-py-tetrahydroquinoline (Example VIII) were the best of thepy-tetrahydroquinolines investigated. They were 30% better thanN-methylaniline on a mole basis.

It will be understood that the additives of the invn tion may beadvantageously utilized in any hydrocarbon fuel suitable for use ininternal combustion engines of the spark-ignition type. In general,these fuels are comprised of mixtures of hydrocarbons having suitablevolatility characteristics. For example, automotive gasolines generallycomprise hydrocarbon mixtures having initial boiling points of around F.and end-boiling points of around 440 F. and which boil substantiallycontinuously between these points. These motor gasolines usually show aclear octane number of from about 70 to about 90.

Aviation gasolines, on the other hand, are mixtures of hydrocarbonswhich have an initial boiling point of around 80 F. and an end boilingpoint of about 330 F. and which boil substantially continuously betweenthese points. Aviation fuels have octane ratings of from about 80 toabout 100.

The data in Table III illustrate the octane rating improvement obtainedby the use of py-tetrahydroquinoline in two types of base fuels, asfollows.

Fuel A is a blend of 70% catalytically-cracked and 30%thermally-reformed gasolines having an initial boil ing point of 104 F.,a 50% point of 226 F. and a point of 350 F.

Fuel B is a catalytically-reformed gasoline. It contained 44% parafiin,3% olefin and naphthalene and 53% aromatics. It had an initial boilingpoint of F., a 50% point of 250 F. and a 90% point of 320 F.

TABLE HI Research octane number (F-l) Fuel blend Clear 3 cc. TEL/ gal.

BaseFue1 A 83. 3 93. 2 Fuel A+1.5% py-tetrahydroqninoline 87. 6 95.9BaseFuel B 89.0 97.7 Fuel B+3% py-tetrahydroquinoline 95. 2 iso+0. 13

1 Indicates fuel of same value as isooctane plus 0.13 ml. TEL.

The anti-knock action of thecompounds of the present invention isindependent of other anti-knock agents of either the metallic ornon-metallic type. Hence, they can be used to increase the octaneratings of fuels containing other anti-knocks.

Other additives designed to impart various improved properties to thefuel may also be used in the fuels containing the anti-knock agents ofthis invention. Thus, anti-oxidants, metal deactivators, anti-rust,anti-stalling and ignition control compounds may be used in the fuelcomposition.

The amount of the additives of the invention which is added to thegasoline will depend upon the particular gasoline and the amount ofimprovement desired. In general, from about 0.1% to about 10%, byweight, of additive may be used. Also, as indicated herein, theadditives of the invention are advantageous when used in the fuels inconjunction with tetraethyl lead. In general, the amount of tetraethyllead to be used in conjunction with the new additives may range fromabout 0.1 cc. to about 10 cc. per gallon. The conjoint use of the newadditives and tetraethyl lead is particularly indicated where aviationgasolines of high octane ratings are desired.

Although the present invention has been illustrated herein by means ofspecific embodiments and examples, it is not intended that the scope ofthe invention be limited thereby but only as indicated in the followingclaims.

We claim:

1. A gasoline containing a minor amount, from about 7 0.1% toabout 10%,by weight, of a compound having the general formula MAW I n f where R isselected from the group consisting of hydrogen, alkyl groups containingfrom 1 to about 4 carbon atoms and alkoxy groups having from 1 to about4 carbon atoms, with not more than three R groups, other than hydrogen,being substituted on the non-aromatic ring and n represents an integerselected from and 1.

2. A gasoline containing a minor amount, from about 0.1% to about byweight, of tetrahydroquinoline.

3. A gasoline containing a minor amount, from about 0.1% to about 10%,by weight, of 1,2-dihydroindo1e.

4. A gasoline containing a minor amount, from about 0.1% to about 10%,by weight, of .8-methyl-py-tetrahydroquinoline.

5., A gasoline containing a minor amount, from about 0.1% to about 10%,by weight, of 6-methyl-py-tetra hydroquinoline.

6. A gasoline containing a minor amount, from about 0.1% to about 10%,by weight, of 6-methoxy-py-tetrahydroquinoline.

7. A gasoline containing from about 0.1 cc. to about 10 cc. per gallonof tetraethyl lead and from about 0.1% to about. 10%, by weight, of acompound having the where R is selected from the group consisting ofhydrogen, alkyl groups containing from 1 to about 4 carbon atoms andalkoxy groups having 1 to about 4 carbon atoms, with not more than threeR groups, other than hydrogen, being substituted on the non-aromaticring and n represents an integer selected from O and 1.

8. A gasoline containing from about 0.1 cc. to about 10 cc. per gallonof tetraethyl lead and from about 0.1% to about 10%, by weight, oftetrahydroquinoline.

9. A gasoline containing from about 0.1 cc. to about 10 cc. per gallonof tetraethyl lead and from about 0.1% to about 10%, by weight, of1,2-dihydroindole.

10. A gasoline containing from about 0.1 cc. to about 10 cc. per gallonof tetraethyl lead and from about 0.1% to about 10%, by weight, ofS-methyl-py-tetrahydroquinoline.

11. A gasoline containing from about 0.1 cc. to about 10 cc. per gallonof tetraethyl lead and from about 0.1% to about 10%, by weight, of,-methyl-py-tetrahydroquinoline.

12. A gasoline containing from about 0.1 cc. to about 10 cc. per gallonof tetaethyl lead and from about 0.1% to about 10%, by weight, of6-methoxy-py-tetrahydroquinoline.

References Cited in the file of this patent UNITED STATES PATENTS2,030,033 McConnell Feb. 4, 1936 2,560,898 Schulze et a1. July 17, 19512,647,824 Jones et a1. Aug. 4, 1953 2,787,551 Bell et a1 Apr. 2, 1957

1. A GASOLINE CONTAINING A MINOR AMOUNT, FROM ABOUT 0.1% TO ABOUT 10%,BY WEIGHT, OF A COMPOUND HAVING THE GENERAL FORMULA